The manufacture of multi-paned window lights for use in the glazing of windows and doors requires that a controlled insulative distance be kept between the adjacent glazing panel panes. Ideally, this gap distance should be defined by a peripheral frame, which is hermetically sealed to the spaced apart panes thus creating a confined "dead air" space, which may be optionally filled with an improved insulative gas.
Such spacer frames have usually been roll-formed, using tubular type aluminum profile sectioned frame materials, the hollow interior of which frequently serves to receive moisture vapor desiccants, for the removal of any moisture that may be present within the sealed construction. While such metal spacers form an effective moisture vapor barrier, they also possess high thermal conductivity characteristics, with a conductivity coefficient "k" value in excess of 117 which creates a thermal bridge between the panes being separated. This construction is responsive to dew point levels and can lead to the accumulation of moisture, as condensation and frost around the glazing panel periphery. Such accumulations are undesirable aesthetically as well as being potentially destructive to adjoining structures, due to staining and moisture damage.
Thermally insulative spacers have been made from thermosetting and thermoplastic materials by the pulltrusion or extrusion process, which indeed have overcome the thermal insulative problem, but have failed to durably respond to the requirements of low gas permeability, resistance to sunlight degradation due to the action of ultra-violet light energy and have caused internal "fogging" of the glazing panel due to outgassing of hydrocarbon vapours from the plastics used, which can condense on the internal faces of the inner and/or outer panes. The developing use of special glazing glasses has tended to exacerbate ultra-violet degradation, tending to reflect and build up the ultra-violet level.
It will be further understood that, in addition to thermal insulation and gas encapsulation and retention performance, which are particularly important, the requirement also exists for practical, low cost, effective spacers that require a minimum of waste during fabrication, lend themselves to ready formation and installation, and which provide for the incorporation of absorbents for moisture vapor and other, hydrocarbon gases, to extend the service lifespan of a sealed, insulative glazing panel.
Various aspects of the prior art are to be found in the following United States patents which are directed to multipaned window systems and components thereof.
______________________________________ 49,167 August 1865 Stetson 3,314,204 April 1967 Zopnek 3,280,523 October 1966 Stroud et al. 4,015,394 April 1977 Kessler 4,109,431 August 1978 Mazzoni et al. 4,658,553 April 1987 Shingawa 4,719,728 January 1988 Erikson et al. 4,649,685 March 1987 Wolf et al. 4,567,841 March 1986 Lingemann 4,564,540 January 1986 Davies et al. 4.226,063 October 1980 Chenel 4,222,213 September 1980 Kessler 4,113,905 September 1978 Kessler 4,198,254 April 1980 Laroche et al. 3,965,638 June 1976 Newman 3,935,683 February 1976 Derner et al. ______________________________________
In various solutions, ranging from Stetson to Derner et al., various aspects of spacer provisions, and of their respective limitations may be fairly readily identified. In addition to complexity, the costing aspects of each spacer system must be born in mind as well as the need to extend the sealing life expectancy of the spacer. Only an established, long term life of several years duration can effectively validate the longevity of seal effectiveness that may be achieved by a particular system.
A further, highly significant aspect of any such spacer system is its suitability for assembling into a window unit. Factors such as ease of handling; handling robustness; longitudinal and lateral stiffness; ease of cutting to length and facility for forming joints, particularly corner joints; suitability for applying adhesives to selected surfaces, are all relevant factors in determining the suitability of spacer elements.
In the case of pultruded, glass reinforced plastic sections, these are generally of considerable thickness, which complicates corner formation. These sections generally possess an unacceptably high gas permeability, while also tending to emit hydrocarbon vapours into the sealed space between the glazing panes. They are also a comparatively high cost item.
Extruded and roll formed metal sections, which are widely used, create a highly conductive thermal bridge, leading to dew line formation.
In reviewing the various aspects of the prior art it should be born in mind that an ideal spacer should be of low cost; should possess extremely high resistance to gas percolation therethrough; be suitably constituted to traverse the corners of the panes; possess high resistance to degradation; be laterally flexible, readily applied, and effectively adhered and edge- sealed; structurally stable; of sufficient mechanical strength for installation; and possessing a low edge-to-edge thermal conductivity factor.
Costs have been known to run as high as ninety cents Canadian per lineal foot, for a compound aluminium/plastic section, constituting a thermally broken aluminum seal.